1. Field of the Invention
This invention relates to an improved method and apparatus for texturizing yarn. In a further aspect, the invention relates to a texturizing process, and apparatus therefor, for simultaneously texturizing two or more yarns and winding said yarns on a single winder roll. In another aspect, this invention relates to an improved texturizing system for texturizing two or more yarns having a unique control-sensing system wherein the relative tensions on said yarns are sensed with respect to an upper value (yarn tightness) and a lower value (yarn slack) and in response thereto to rate of yarn takeup and respective yarn lengths are adjusted to effectuate simultaneous wind-up of two or more yarns of substantially equal length on a single roll. In still another aspect, the invention relates to fluidized crimping and bounce crimp texturizing.
2. The Prior Art
Synthetic thermoplastic yarn materials are produced as a number of continuous, straight, smooth filaments. Such yarns have little bulk, and their utility in textile applications is thus rather limited.
In order to enhance the bulk and texture of synthetic yarns, a variety of crimping processes have been used in the past. One common technique which has been used for thermoplastic yarns is to bend the yarn filaments and heat the yarn while the filaments are in bent or crimped configurations, commonly referred to as false twist texturizing; note, for example, U.S. Pat. Nos. 3,932,986 and 3,946,546. Another type of texturizing is fluidized texturizing such as, for example, described in U.S. Pat. No. 2,869,967 and stuffer box crimping such as, for example, described in U.S. Pat. No. 4,081,886.
One especially good texturizing technique, in terms of yielding a high-bulked yarn, is known as "rebound" or "bounce crimping" such as for example described in U.S. Pat. No. 3,665,567.
It would be very desirable to increase the production of a given yarn processing apparatus by simultaneously processing (e.g., texturizing) two or more yarns. On its face, it would seem that this could be effectuated by merely adding additional texturizing units and then winding all of the processed yarns in discrete packages on a common winder spindle. However, it has been found that the yarns issuing from the respective texturizers are not equal in length thus producing an imbalance which ultimately causes yarn damage and makes an unusable yarn package. One way to obviate this problem would be to use separate winders, but as the winder is one of major components of the yarn processing apparatus, both in terms of cost and size, there would be little advantage to this over simply using an individual yarn processing apparatus for each yarn.
The invention which will be subsequently described, can be especially advantageously applied to bounce crimping. Bounce crimping entails hurling yarn, propelled by a heated fluid through a jet, in a continuous stream-like flow against a foraminous surface upon which the yarn impinges and from which the yarn instantaneously rebounds or bounces. The impact of the yarn upon the foraminous surface axially buckles and crimps individual filaments of the yarn while the heated fluid passes through the foraminous surface. The texturized yarn progresses without tension and substantially by rebound inertia away from the crimping zone and, in the original prior art process, was guided to a collection station where the yarn was heated and then cooled to heat-set the crimp prior to winding upon a storage spool.
Thermoplastic yarn texturized by the foregoing bounce crimping process possesses, inter alia, exceptional covering power.
Although, bounce crimping produces a particularly desirable product, the process has certain sensitivities. Thus, in order to properly conduct bounce crimping, it is important that the yarn is rebounded from the screen and discharged from the bounce crimper under essentially no tension. The yarn cannot be pulled from the bounce crimper, since tension on the yarn at this point could pull the crimp from the yarn and could also cause the foraminous screen to be bypassed.
Various improvements in bounce crimp texturizing processes and apparatus are described in U.S. Pat. Nos. 3,859,696, 3,859,697, 3,879,819 and 3,887,971. All of the apparatus and processes described in these patents and in U.S. Pat. No. 3,665,567 are characterized by the use of a J-tube type yarn accumulator wherein the yarn is accumulated (piled) and heat-treated (heat-set and cooled). In U.S. Pat. No. 3,879,819, the J-tube is provided with a photo-cell light sensing means for maintaining a contain height (pile) of yarn in the J-tube by regulating the yarn wind-up speed in response to the sensing means.
The J-tube accumulator was used by the prior art to heat-set the crimp in the yarn and to ensure that the yarn rebounded from the bounce crimp screen in a tensionless state by permitting the yarn to free-fall into the J-tube accumulator. Subsequently, the J-tube was primarily used only for the second purpose. However, in accumulating or piling the yarn, tangles were found to occur, resulting in localized pulling on the yarn as it was wound up, thus causing the crimp to be pulled out of random segments of the yarn and/or the yarn to break. The frequency of these breaks also necessitates an increase in the number of operators required to operate or monitor a given number of texturizing machines and rethread the yarn when breaks occur.
Also, where low-denier yarns (e.g., about 500 denier or less) are used, the problem is magnified such that accumulator systems cannot be efficiently used. This magnification is believed caused by the fact that the lower the denier, the more loops or coils that are in contact with each other in the accumulator. Hence, the more contact, the more chance there is for filaments of the various loops to tangle with each other. This increased contact, coupled with the lower weight of the loops or coils, substantially increases the likelihood of the loops being pulled out of the accumulator, resulting in increased piling and tangles, etc.
In my copending application, Ser. No. 967,449, filed Dec. 7, 1978, now U.S. Pat. No. 4,226,010, I disclosed a method and apparatus for collecting (winding) the yarn from the bounce crimp texturizer without tensioning the yarn in the critical area and without significantly accumulating (piling) the yarn which substantially eliminated the tangling problems of the prior art processes.
In my copending application U.S. Ser. No. 46,730 filed on June 7, 1979, I disclosed an accumulatorless bounce crimping texturizing process and apparatus using a novel tension-slack sensing and control system which also eliminates the afore-discussed tension and yarn tangling problems.